With the expansion of telecommunication and computer technology, increasing amounts of electronic equipment are required at businesses and other facilities. Large amounts of electronic equipment are often stored in a room devoted to that purpose. As shown in FIG. 1, the equipment is generally organized in a cabinet 2 of standard dimensions with multiple horizontal trays 4 to support multiple rows of equipment. The cabinet 2 generally includes sides, 6, back 8, top 10, bottom 12, and a door 14 to gain access to the equipment therein. Power rails, uninterruptible power supplies, and other features can be included. This equipment generates heat, which must be removed from the room in order to maintain stable conditions in the rooms. Because advances in technology have lead to an increased density of the amount of electronic equipment that can be provided in a set amount of space, it has become increasingly difficult to remove this heat by means of the conventional room air conditioning alone. Therefore, it is often necessary to install localized cooling for the cabinets that house this electronic equipment.
General purpose cooling systems for rooms and open spaces are often inadequate for single racks of critical electronic equipment. Cooling systems designed for room size data centers may be adequate for overall critical equipment needs in the data centers, but are often too large for single stacks of equipment in a single cabinet. Such cooling systems generally use an external connection for heat rejection, for example, with chilled water or a cooling tower.
Some existing commercial suppliers have provided a closed loop refrigerated cooling system coupled to the cabinets. The refrigeration system typically includes a compressor for compressing refrigerant in the system to an elevated pressure, a condenser to cool the refrigerant that is heated by the act of compression, an expansion device that thermodynamically cools the refrigerant, an evaporator that is cooled by the cooled refrigerant flowing therethrough, a fan to move air across the evaporator's surfaces to cool the air whereby the refrigerant in turn absorbs heat from the warmer air, various refrigeration lines for carrying the refrigerant between the components, and a system controller, such as a thermostat. These systems are generally mounted in the bottom or on top of the cabinet. A typical cabinet is about 24″ wide and 78″ to 84″ high. The cooling module can consume about 12″-15″ in the bottom of the cabinet or add such amount to the overall height if mounted on top of the cabinet.
While these systems have been well received in the marketplace, they were designed for cooling capacities of electronic equipment up to about 3.0 KW. The cooling capacity of these existing electronic equipment cabinets with self-contained cooling solutions are insufficient for some newer computing devices, which consume more power and produce higher levels of heat. Some of the power requirements require a cooling capacity many times the existing amounts approaching an order of magnitude change, such as 10 KW to 15 KW. Simply making the cooling system bigger would consume about half of the cabinet space or, if mounted on the top, would cause clearance problems with room ceilings—both commercially unsatisfactory solutions.
Also, existing computer equipment cabinets with built-in cooling coils and fans do not provide satisfactory means of ventilation when the cooling system fails. These existing solutions typically use cabinet doors designed to open outwardly automatically for ventilation if there is a failure in the cooling system. However, such systems are subject to doors being blocked, rendering the emergency cooling means ineffective. One known backup solution is mounted to a vertical portion of the cabinet with a damper that opens inwardly. Air flows downwardly, across the bottom of the unit, up the wall opposite the entering wall, across the top, down the entering wall, and out an exit. The damper is limiting and the length of the airflow causes inefficient removal of the generated heat.
Another challenge with existing electronic equipment cabinets with built-in cooling coils and fans is that they typically do not respond quickly to large, instantaneous changes in heat load. The cooling system senses the heat after the heat has been generated and then attempts to compensate by extra cooling to lower the temperature back down to an intended set point. The cooling system is therefore responsive to thermal heat after it has been produced. The result can be a wide fluctuation of temperatures in the cabinet, as the cooling system's control system responds to the load change.
Therefore, there remains a need for an improved cooling system for electronic equipment cabinets.